Intramolecular CâF Activation in Schiff-Base Alkali Metal Complexes

Article Cite This: Organometallics XXXX, XXX, XXX−XXX

pubs.acs.org/Organometallics

Intramolecular C−F Activation in Schiff-Base Alkali Metal Complexes Francisco M. García-Valle, Vanessa Tabernero, Tomás Cuenca, Marta E. G. Mosquera,* and Jesús Cano* Departamento de Química Orgánica y Química Inorgánica, Instituto de Investigación en Química “Andrés M. del Río” (IQAR), Universidad de Alcalá, Campus Universitario, 28871-Alcalá de Henares, Spain

Downloaded via TULANE UNIV on February 6, 2019 at 19:41:20 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

S Supporting Information *

ABSTRACT: A series of alkali metal complexes (Li, Na, K) with different fluorinated phenoxo-imine ligands [M{(O-2(RNCH)-C6H4}] [R = C6F5; 2,4,6-F3C6H2F3; 2,6-C6H3F2; 2,3-C6H3F2; 2-C6H4F; 2-CF3C6H4CH2; CF3CH2] have been synthesized and fully characterized. By using THF as solvent, suitable crystals for X-ray diffraction analysis were obtained, and the solid state structure of some of the prepared compounds has been determined. This analysis reveals the formation of a C−F bond activation product for the potassium compound with the five-fluorinated ligand. In stronger donor solvents, such as dimethylsulfoxide, this process occurs immediately, independently of the metal used. This C−F activation takes place in a smooth process at room temperature. The nature of this reaction is studied by 1H-DOSY NMR experiments with stoichiometric amounts of DMSO, monitoring the disaggregation process from the initial solution structure to the final activation product. The variation of the number of fluorine atoms and their location in the iminic ring is also studied, showing their influence in this intramolecular C−F bond activation process.

■

INTRODUCTION The synthesis of new fluoroaromatic compounds via C−F bond activation has demonstrated to be important in several applications such as pharmaceuticals, pesticides, or advanced organic materials.1 As well, the possibility to cleave this bond is crucial toward the degradation of fluorocarbons as a remediation of their associated environmental problems. The carbon fluorine (C−F) bond is the strongest bond formed by carbon and any other element. The bond dissociation energy makes the C−F bond relatively inert and stable, especially in aromatic rings (CH3−F = 115 kcal·mol−1; CH3−H = 105 kcal· mol−1; Ph−F = 127 kcal·mol−1).2 Furthermore, when directed toward different organic transformations, a large number of C−F bond activations are able to form new C−C bonds, although, in the presence of X− species (O−, S−, N−), the formation of C−X bonds may take place. The nature of these transformations has been widely discussed in several reviews where a wide variety of approaches have been described.3 Recently, the selective and catalytic C−F bond cleavage mediated by transition metal complexes has been reported.4 However, the use of transition metals implies several drawbacks in industry, due to high costs, purification processes, or metal toxicity which can be found in the final products. In consequence, the use of metals with less toxicity such as some group s metals is of great interest. In fact, these metals have been employed successfully in C−F bond cleavage reactions.5 As such, the nucleophilic aromatic substitution reaction (SNAr) of fluoroarenes via transition metal-free C−F © XXXX American Chemical Society

bond activation emerges as a greener and more sustainable procedure for a broad type of substrates.6 In general, the group s metal compound deprotonates the nucleophile, and the MNu species formed reacts with the fluoroarene to give a C−F bond activation and generate the corresponding C−Nu bond (Figure 1).6a−e However, depending on the base strength or the fluoroarene substitution, other mechanism pathways have been observed.7 Transition metal-free C−F bond activation has been widely used in the production of heterocyclic compounds via intramolecular cyclization using gem-difluoroolefins, affording 5- and 6-membered heterocycles, and more recently 7membered rings.8 The synthesis of heterocycles from

Figure 1. Nucleophilic aromatic substitution of fluoroarenes. (a) General procedure. (b) Intramolecular procedure. Received: November 30, 2018

A

DOI: 10.1021/acs.organomet.8b00868 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics fluoroarenes as starting materials via an intramolecular SNAr reaction is also a plausible and fast pathway; however, it has been rarely reported.9 In this context, the use of group s metals as transition metal-free agents is the most promising approach to achieve these organic transformations (Figure 1b). Schiff bases are very popular ligand precursors due to their versatility and ease of preparation. We have already reported several main group metal based complexes stabilized by the presence of Schiff bases derived ligands with different steric hindrance10 that are very active in polymerization processes. However, the introduction of fluorine atoms in these compounds has been scarcely reported, and only one example of an alkali metal derivative has been found.11 The possibility of an intramolecular SNAr reaction, as shown in Figure 1, prompted us to study this kind of compounds. Herein, we report the synthesis and characterization of a series of fluorinated Schiff bases and their alkali metal derivatives. These compounds give an intramolecular C−F bond activation in the appropriate conditions, generating 7-membered heterocyclic compounds. Moreover, the cleavage of the C−F bond is straightforward and takes place at room temperature. To our knowledge, this is one of the few cases that this C−F activation is carried out in such mild conditions.7f,g

■

RESULTS AND DISCUSSION By using reported synthetic methods,10 we have prepared the perfluorinated Schiff base {La}H in high purity and good yield.12 The 1H, 13C, and 19F NMR spectra confirm the formation of this compound. The stoichiometric reaction between {La}H and the corresponding metallic precursor, [Li{N(SiMe3)2}], NaH, or [K{N(SiMe3)2}], in toluene gives rise to the expected compounds (1−3)a (Scheme 1). After removing the solvent, the resultant solids are washed in hexane to eliminate the reaction byproducts and highly pure alkali metal compounds are isolated (Scheme 1).

Figure 2. Top: ORTEP plot for 2a showing thermal ellipsoids plots (30% probability). Hydrogen atoms are omitted for clarity. Bottom: Core view.

Scheme 1. Synthesis of the Alkali Metal Compounds stituted by four metallic atoms bridged by the oxygen atoms of the Schiff bases, and gives a Na4O4 cubic core. The Na−O−Na angles (from 85.59(11)° to 93.45(11)°) are close to 90°, in agreement with the cubic arrangement. This class of solid state structures have been already described for sodium compounds,13 although, to the best of our knowledge, this is the first structure reported of a fluorinated Schiff base alkali metal compound. Both the nitrogen and the ortho fluorine atoms establish a donor interaction with the sodium. The metal completes its coordination sphere by coordinating one THF molecule, and shows a distorted octahedral environment. The Na−O bond lengths are within the usual range found in the literature for this type of sodium compounds (see Table 1). The shortest Na−O distances are those corresponding to the donor interaction between the metal and the THF, whereas the distances with the oxygen bridging atoms from the ligands are slightly longer. Concerning Na···F interactions, the bond lengths are remarkably different in the same molecule (Na1··· F6 = 2.5515(18) Å and Na2···F5 = 2.632(2) Å) and are quite short and within the range observed in the literature (2.237− 3.739 Å).11b In this case, no lengthening of C−F distance could be noticed in comparison with the fluorinated Schiff base.12a A THF-d8 solution of compound 3a has also been analyzed by NMR techniques, and surprisingly, the formation of a different compound than the expected and previously

The final products are characterized in solution by NMR spectroscopy and in the solid state by elemental analysis. The 1 H and 19F NMR spectra are recorded in C6D6 and display a series of broad signals due to the poor solubility of the compounds, but good enough to confirm the formation of (1− 3)a (Figure S1; see Supporting Information). Three signals corresponding to the different kinds of fluorine atoms (ortho, meta, and para) present in the complexes are observed in the 19 F NMR spectra. For 2a and 3a, a similar pattern in the spectra can be noticed due to a higher similarity between the metallic centers. However, for 1a, the spectrum is quite different and shows one signal low-field shifted that belongs to the ortho fluorine atoms, probably reflecting the presence of an interaction with the metal. The addition of THF as solvent led to the isolation of suitable single crystals for X-ray crystallographic analysis for 2a. The solid state structure for 2a is shown in Figure 2. The molecular structure reveals a tetranuclear disposition conB


Article

Organometallics Table 1. Selected Bond Lengths (Å) and Angles (deg) for 2aa bond lengths (Å) Na(1)−O(2) Na(1)−O(2)#1 Na(1)−O(1) Na(1)−O(3) Na(1)−N(2) Na(1)···F(6) N(2)−C(22) F(6)−C(1)

2.324(2) 2.359(2) 2.383(2) 2.441(2) 2.505(2) 2.551(2) 1.284(3) 1.346(3)

Na(2)−O(1)#1 Na(2)−O(1) Na(2)−O(4) Na(2)−O(2) Na(2)−N(1) Na(2) ···F(5) N(1)−C(6) F(5)−C(2)

2.322(2) 2.321(2) 2.400(2) 2.417(2) 2.492(2) 2.632(2) 1.291(3) 1.356(3)

angles (deg) O(2)−Na(1)−O(2)#1 O(2)−Na(1)−O(1) O(2)#1−Na(1)−O(1) O(2)−Na(1)−O(3) O(2)#1−Na(1)−O(3) O(1)−Na(1)−O(3) O(2)−Na(1)−N(2) O(2)#1−Na(1)−F(6) O(1)−Na(1)−F(6) O(3)−Na(1)−F(6) N(2)−Na(1)−F(6)

85.74(7) 92.89(7) 93.19(7) 99.08(8) 103.11(8) 160.37(8) 73.24(7) 135.89(7) 83.63(6) 77.07(7) 65.04(7)

O(1)#1−Na(2)−O(1) O(1)#1−Na(2)−O(4) O(1)−Na(2)−O(4) O(1)#1−Na(2)−O(2) O(1)−Na(2)−O(2) O(4)−Na(2)−O(2) O(1)#1−Na(2)−N(1) O(1)−Na(2)−F(5) O(4)−Na(2)−F(5) O(2)−Na(2)−F(5) N(1)−Na(2)−F(5)

85.54(7) 97.35(8) 102.45(8) 93.35(7) 91.93(7) 162.65(9) 72.80(7) 137.94(7) 78.16(7) 84.68(7) 63.81(7)

Symmetry transformations used to generate equivalent atoms: #1 −x, y, −z + 1/2.

a

characterized is detected. Figure 3 shows a comparative 19F NMR spectrum of compound 3a in C6D6 and the new

Figure 4. ORTEP plot for Ox1 showing thermal ellipsoids plots (30% probability). Hydrogen atoms are omitted for clarity.

Table 2. Selected Bond Lengths (Å) and Angles (deg) for Ox1 Figure 3. Comparative 19F NMR spectra of compound 3a in C6D6 (a) and THF-d8 (b) with the suggested formed compounds.

bond lengths (Å) N(1)−C(7) N(1)−C(15) O(1)−C(10) O(1)−C(1) C(1)−C(2) C(1)−C(6) C(6)−C(7)

compound generated in THF-d8 solution. The 19F NMR spectrum in THF-d8 shows now four resonances (Figure 3b) that correspond to four different fluorine atoms instead of the three expected according to that observed in C6D6 solvent (Figure 3a). According to these spectroscopic data and the elemental analysis, the formation of 6,7,8,9-tetrafluorodibenzo[b,f ][1,4]oxazepine (Ox1) is proposed. Suitable single crystals from a THF solution of Ox1 were obtained to be studied by X-ray diffraction techniques (Figure 4, Table 2). This study confirms the structure suggested on the basis of the NMR and elemental analysis data. As shown in Figure 4, the solid state structure demonstrates that, in THF solution, compound 3a goes through a C−F ortho bond activation that leads to the formation of a dibenzoxazepine. Interestingly, under these conditions, this intramolecular C−F bond cleavage occurs only from the potassium complex 3a, while 1a and 2a remain unchanged. Dibenzoxazepines are very interesting derivatives in medicinal chemistry due to their biological and pharmacological activity.14 However, catalytic

1.274(5) 1.405(5) 1.379(4) 1.404(4) 1.363(6) 1.390(5) 1.465(5)

angles (deg) C(7)−N(1)−C(15) C(10)−O(1)−C(1) C(6)−C(1)−O(1) C(1)−C(6)−C(7) N(1)−C(7)−C(6) O(1)−C(10)−C(15) C(10)−C(15)−N(1)

121.9(3) 115.3(3) 119.8(3) 124.0(3) 130.7(4) 122.8(3) 126.3(3)

asymmetric methodologies for the synthesis of chiral dibenzoxazepines are uncommon.15 Influence of the Solvent. In order to obtain a better understanding over the intramolecular C−F bond activation process and to promote that the lithium 1a and sodium 2a derivatives could also go through this C−F bond activation, a stronger donor solvent such as DMSO was employed. Under these conditions, the formation of Ox1 is detected by 1H and 19 F NMR experiments. As such, when 1a and 2a are dissolved in DMSO-d6, the spectra registered immediately display an identical set of signals than the previously recorded for the isolated crystals of Ox1 obtained from the THF solution of 3a C


Article

Organometallics (Figure S5 in the SI). This evidence confirms that an intramolecular SNAr of the fluorine atom in the ortho position for 1a and 2a takes place in the presence of dimethylsulfoxide. As expected, when 3a was dissolved in DMSO, the Ox1 product was also formed immediately. On the basis of these results, the reaction pathway for this SNAr reaction for the fluoroaromatic compound {La}H mediated by different alkali metals is proposed in Scheme 2. Scheme 2. Proposed Reaction Pathway Based on the Experimental Results

Figure 5. 1H-DOSY NMR spectra of complex 2a recorded in THF-d8 (see SI). The internal reference standards were N-benzylideneaniline (PhNCHPh; FW = 181.2), 1-phenylnaphthalene (PhN, FW = 204.7), and 1,2,3,4-tetraphenylnaphthalene (TPhN, FW = 432.6).16

The reaction may start with the formation of an alkoxoimino alkali metal complex.10 This compound exhibits an M··· F interaction as observed in the crystalline structure of 2a. This interaction might increase the electrophilicity of the carbon atom, which then becomes more susceptible to the nucleophilic attack by the oxygen atom bound to the alkali metal. This nucleophilic attack leads to the formation of the intramolecular cyclization product and the corresponding salt MF. It is noteworthy that this behavior is preferably observed for strong donor solvents such as dimethylsulfoxide or THF. These reaction media probably have the ability of increasing the C−F bond polarity, which may favor the subsequent nucleophilic attack of the oxygen atom, the M−F bond formation, and the intramolecular cyclization compound generation. The activation process also takes place when the reaction is performed as one pot using THF or DMSO as solvents (Scheme 3).

dimeric and the monomeric derivative resulting from the fragmentation process (Figures S6 and S7, Table S3; see Supporting Information). When another equivalent of DMSOd6 is added, the NMR experiment shows again the presence of two compounds. Now, the dimeric compound has disappeared completely and only the monomeric is detected together with another species that match the C−F bond activation product (Figures S8 and S9, Table S4; see Supporting Information). After 24 h, it is not possible to identify the signals belonging to the initial sodium complex or the monomeric species and only the C−F bond cleavage derivative is observed. This experimental evidence is collected in Scheme 4. Scheme 4. Diffusion-Ordered NMR Spectroscopy Experiments in THF-d8a

Scheme 3. Reaction Ways and Products Based on the Experimental Resultsa

a

Conditions: (a) Complex/solvent: 1a−2a/THF. (b) Complex/ solvent: 3a/THF; (1−3)a/DMSO.

a

For a more in-depth investigation over this process, the reaction between compound 2a in THF-d8 and different amounts of DMSO-d6 at room temperature has been investigated through a series of Diffusion-Ordered NMR SpectroscopY (DOSY) experiments. First, the aggregation state in solution of compound 2a (Figure 5) was studied employing the same strategy as the one previously described in the literature.10,16 In these conditions, complex 2a shows a dimeric nature in THF (Figure S3, Table S1; see Supporting Information).10a Then, 1 equiv of DMSO-d6 was added and quickly analyzed, but no changes in the aggregation state of this compound were noticed (Figures S4 and S5, Table S2; see Supporting Information). However, after 72 h, a disaggregation process is observed, and two different species are identified, the

The presence of coordinated solvent has been omitted for clarity.

From these results, it can be deduced that the role of the solvent is crucial in this process, leading to the disaggregation of the multinuclear alkali metal compound and promoting the C−F bond activation reaction. Fluorine Substituents Influence. Encouraged by the obtained results when the Schiff base {La}H has been used, we considered the introduction of a variable number of fluorine atoms in the ring to analyze their influence on the C−F activation reactivity. In consequence, a series of Schiff base compounds and their alkali metal derivatives have been synthesized and fully characterized following the same procedure as that for {La}H and (1−3)a (see Figure 6). D


Article

Organometallics

> C6H2F3 > C6H3F2 > C6H4F). The position of the fluorine atoms also has an important effect on the reactivity and modifies the reaction rates as observed for {Lc}H and {Ld}H. For these compounds, the reaction occurs faster if both fluorine atoms are in ortho positions than if they are placed in ortho and meta. We also confirmed that the metal effect is a very important factor, following the general trend of reactivity K > Na > Li, already reported by Diness et al.6c in the N-arylation of azoles and indoles from unactivated monofluorobenzenes which could be related to a higher ionic character for the potassium compounds. Finally, for Schiff bases synthesized with a trifluoromethyl group, such as {Lf}H or {Lg}H, the C−F bond activation does not take place as consequence of the different C(sp3) nature of the carbon atom.

Figure 6. (a) Fluorinated Schiff bases. (b) Alkali metal derivatives.

The C−F bond activation reaction has been studied following the same conditions as those previously described for 1−3a by using DMSO at room temperature. The results for these tests are summarized in Table 3. As it can be seen, a decreasing number of fluorine atoms in the imine ring produces a slower C−F bond activation and the SNAr reaction, in those cases where the process takes place,17 needs longer reaction times to reach completion. As a result, a general reactivity trend has been found, where perfluorinated substrates are more reactive than less substituted ones (C6F5

■

CONCLUSIONS In summary, we have reported a series of fluorinated Schiff base alkali metal complexes. The five-fluorinated sodium derivative 2a can be isolated, and its crystal molecular structure has been determined by X-ray diffraction analysis. In the structure, an M···F interaction is observed. In the presence of strong donor solvents, these alkali metal compounds (M = Li, Na, K) are able to give, at room temperature, the intramolecular C−F bond activation of the ortho fluor-C bond with the corresponding formation of the cyclization product, the 6,7,8,9-tetrafluorodibenzo[b,f ][1,4]oxazepine Ox1, which was also characterized by X-ray analysis. The 1H-DOSY NMR experiments of the isolated sodium complex 2a let us to detect the disaggregation process and subsequent C−F bond cleavage that takes place in the presence of DMSO, and to confirm its crucial role in the process. This proof leads us to suggest a reaction pathway where the alkali metal establishes an M···F interaction that, in the appropriate conditions, leads to the C− F bond activation. Subsequently, the study with different Schiff bases containing a variable number of fluorine atoms demonstrates that the number and position of the fluorine atoms have an important influence in the activation of the C− F bond. Thus, the lesser fluorine atoms are present in the ring, the harder the reaction is. This intramolecular reaction is an important achievement for these C−F activation processes since the reaction takes place stoichiometrically and at room temperature using group s metals, something which is not usually observed.

Table 3. C−F Bond Formation and Cyclization Productsa

■

EXPERIMENTAL SECTION

General Procedures. Air or water sensitive experiments were performed under an inert atmosphere using an MBraun MB-20G glovebox (O2 < 0.6 ppm) or standard Schlenk-line techniques (O2 < 3 ppm). An MBraun Solvent Purification System was employed to purify solvents. Moreover, deuterated solvents were degassed by freeze−thaw−vacuum cycles and stored in a glovebox in the presence of molecular sieves (4 Å). Fluoroaniline compounds were purchased from Fluorochem and used as received. 2-Hydroxybenzaldehyde and metallic precursors were purchased from Sigma-Aldrich. Sodium hydride was washed twice with dry hexane due to that the commercial reagent is an oil suspension. A Bruker 400 Ultrashield (1H 400 MHz, 13 C 101 MHz, 19F 376 MHz) was used to record NMR spectra. All chemical shifts were determined using the residual signal of solvents and were reported versus SiMe4. All the new described compounds have been characterized by elemental analysis with a PerkinElmer 2400 CHNS/O analyzer Series II. Found values close to the calculated values have been obtained with deviations slightly above 0.4% in some cases. The nature of the substances studied, the

a

Conditions: r.t., DMSO. Li[N(SiMe3)2], NaH, K[N(SiMe3)2]. Determined by 1H and 19F NMR spectroscopy. cNot determined.

b

E


Article

Organometallics

(215.23 g/mol): C 72.55, H 4.68, N 6.51. Found: C 72.47, H 4.87, N 6.76. Synthesis of (2-CF3C6H4CH2NCHC6H4OH), {Lf}H. Following the same procedure as that described for {La}H but with 2(trifluoromethyl)benzylamine (3.840 g, 0.021 mol) and 2-hydroxybenzaldehyde (2.678 g, 0.021 mol). Yield: 5.514 g, 92%. 1H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 13.21 (s, 1H, OH), 7.85 (s, 1H, HCN), 7.42 (m, 1H, ArH), 7.21 (m, 1H, ArH), 7.11−6.90 (m, 5H, ArH), 6.70 (m, 1H, ArH), 4.59 (m, 2H, −CH2−). 13C NMR (C6D6/ THF-d8, 101 MHz, 295 K): δ 167.2 (CN), 161.9 (C−OH), 137.4, 132.8, 132.4, 132.0, 129.8 (Ar−C), 127.4 (CF3), 126.1, 123.8, 119.3, 118.8, 117.4 (Ar−C), 59.6 (−CH2−). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −59.8 (s, 3F, CF3). Anal. Calcd for C15H12F3NO (279.26 g/mol): C 64.51, H 4.33, N 5.02. Found: C 64.79, H 4.32, N 5.24. Synthesis of (CF3CH2NCHC6H4OH), {Lg}H. As described above for {La}H but using 2,2,2-trifluoroethylamine (2.985 g, 0.029 mol) and 2-hydroxybenzaldehyde (3.680 g, 0.029 mol). Yield: 5.231 g, 87%. 1H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 12.49 (s, 1H, OH), 7.64 (s, 1H, HCN), 7.07 (m, 1H, C6H4), 6.94−6.88 (m, 2H, C6H4), 6.67 (m, 1H, C6H4), 3.46 (m, 2H, −CH2−). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 170.8 (CN), 161.6 (C−OH), 133.6, 132.5 (Ar−C), 126.2, 123.4 (CF3, due to complicated 13C−19F coupling), 119.0, 118.7, 117.5 (Ar−C), 59.5 (−CH2−). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −71.5 (s, 3F, CF3). Anal. Calcd for C9H8F3NO (203.16 g/mol): C 53.21, H 3.97, N 6.89. Found: C 53.38, H 4.15, N 6.96. Synthesis of [Li(O-2-{(C6F5)NCH}C6H4)] [Li{La}] (1a). A mixture of {La}H (0.500 g, 1.74 mmol) and Li[N{Si(CH3)3}2] (0.300 g, 1.74 mmol) was prepared in toluene (50 mL) and stirred one night. Then, volatile compounds and the solvent were removed under vacuum and a white powder was obtained. The resultant solid was washed in hexane, filtered, and dried under vacuum. Yield: 0.427 g, 84%. 1H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 8.08 (s, 1H, HCN), 7.19 (m, 1H, C6H4), 7.04 (m, 1H, C6H4), 6.72 (m, 1H, C6H4), 6.43 (m, 1H, C6H4). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 173.5 (CN), 172.4 (C−O), multiplets from 161.1 to 138.0 (C−F, due to complicated 13C−19F coupling), 137.4, 135.6, 129.3, 125.7, 123.5, 122.0, 113.2, 109.2 (Ar−C). 19F NMR (C6D6/ THF-d8, 376 MHz, 295 K): δ −155.1 (bs, 2F, o-F), −163.3 (bs, 1F, pF), −164.4 (m, 2F, m-F). Anal. Calcd for C13H5F5LiNO (293.12 g/ mol): C 53.27, H 1.72, N 4.78. Found: C 53.48, H 1.90, N 5.10. Synthesis of [Na(O-2-{(C6F5)NCH}C6H4)] [Na{La}] (2a). As described for 1a but using {La}H (0.500 g, 1.74 mmol) and NaH (0.042 g, 1.74 mmol). A yellow pale powder was obtained. Yield: 0.442 g, 82%. 1H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 8.03 (s, 1H, HCN), 6.90 (m, 2H, C6H4), 6.26 (m, 2H, C6H4). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 173.7 (CN), 171.9 (C−O), multiplets from 141.9 to 136.1 (C−F, due to complicated 13C−19F coupling), 136.9, 134.2, 129.7, 123.1, 122.2, 111.8 (Ar−C). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −157.3 (bs, 2F, o-F), −164.5 (m, 2F, m-F), −164.8 (m, 1F, p-F). Anal. Calcd for C13H5F5NNaO (309.17 g/mol): C 50.50, H 1.63, N 4.53. Found: C 50.55, H 1.82, N 5.25. Synthesis of [K(O-2-{(C6F5)NCH}C6H4)] [K{La}] (3a). As described aboved for 1a but using {La}H (0.222 g, 0.773 mmol) and K[N{Si(CH3)3}2] (0.162 g, 0.773 mmol). Yield: 0.221 g, 88%. 1 H NMR (C6D6, 400 MHz, 295 K): δ 7.71 (s, 1H, HCN), 6.99 (s, 1H, C6H4), 6.86 (m, 1H, C6H4), 6.39 (m, 1H, C6H4), 5.22 (m, 1H, C6H4). 13C NMR (C6D6, 101 MHz, 295 K): δ 174.0 (CN), 172.2 (C−O), multiplets from 155.3 to 137.7 (C−F, due to complicated 13 C−19F coupling), 138.2, 135.6, 130.0, 123.5, 122.7, 112.0 (Ar−C). 19 F NMR (C6D6, 376 MHz, 295 K): δ −158.9 (m, 2F, o-F), −163.2 (m, 2F, m-F), −164.0 (m, 1F, p-F). Anal. Calcd for C13H5F5KNO (325.28 g/mol): C 48.00, H 1.55, N 4.31. Found: C 47.62, H 1.64, N 4.51. Synthesis of [Li(O-2-{(2,4,6-C6H2F3)NCH}C6H4)] [Li{Lb}] (1b). Using the same method as that described for 1a but employing {Lb}H (0.620 g, 2.47 mmol) and Li[N{Si(CH3)3}2] (0.426 g, 2.47 mmol). Yield: 0.602 g, 95%. 1H NMR (C6D6/THF-d8, 400 MHz, 295

instability in polar solvents necessary for the crystallization, and their tendency to retain small amounts of solvent very difficult to eliminate under the experimental conditions applied justify these deviations. Synthesis of (C6F5NCHC6H4OH), {La}H. A solution of 2,3,4,5,6-pentafluoroaniline (3.863 g, 0.021 mol) and 2-hydroxybenzaldehyde (2.603 g, 0.021 mol) in ethanol (150 mL) was prepared. This mixture was refluxed (100 °C) for 2 days under stirring. Later, it was concentrated under vacuum to 100 mL, and MgSO4 was added to dry the solution. After, it was filtered and concentrated again under vacuum and stored at low temperature one night. A pale yellow powder was obtained and isolated in high yield. Yield: 4.972 g, 83%. 1 H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 12.23 (s, 1H, OH), 8.38 (s, 1H, HCN), 7.18−7.13 (m, 1H, C6H4), 7.10−7.07 (m, 1H, C6H4), 6.95 (m, 1H, C6H4), 6.72−6.68 (m, 1H, C6H4). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 171.3 (CN), 162.2 (C−OH), multiplets from 142.4 to 137.0 (C−F, due to complicated 13C−19F coupling), 135.2, 133.6, 123.9, 119.6, 119.2, 118.0 (Ar−C). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −153.1 (dd, 2F, o-F), −160.3 (t, 1F, p-F), −164.0 (m, 2F, m-F). Anal. Calcd for C13H6F5NO (287.19 g/mol): C 54.37, H 2.11, N 4.88. Found: C 54.36, H 2.00, N 5.07. Synthesis of (2,4,6-C6H2F3NCHC6H4OH), {Lb}H. Using the same procedure as that described for {La}H but employing 2,4,6trifluoroaniline (3.320 g, 0.022 mol) and 2-hydroxybenzaldehyde (2.729 g, 0.022 mol). Yield: 4.513 g, 82%. 1H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 12.95 (s, 1H, OH), 8.22 (s, 1H, HCN), 7.06− 7.01 (m, 2H, C6H2), 6.82 (m, 1H, C6H4), 6.60 (m, 1H, C6H4), 6.23− 6.15 (m, 2H, C6H4). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 168.6 (CN), 161.9 (C−OH), multiplets from 160.9 to 154.5 (C−F, due to complicated 13C−19F coupling), 134.0, 132.8, 122.3, 119.1, 118.8, 117.7, 100.5 (Ar−C). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −111.0 (s, 1F, p-F), −120.1 (s, 2F, o-F). Anal. Calcd for C13H8F3NO (251.21 g/mol): C 62.16, H 3.21, N 5.58. Found: C 62.34, H 3.30, N 5.71. Synthesis of (2,6-C6H3F2NCHC6H4OH), {Lc}H. As described above but using 2,6-difluoroaniline (3.710 g, 0.028 mol) and 2hydroxybenzaldehyde (3.474 g, 0.028 mol). Yield: 5.735 g, 88%. 1H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 12.92 (s, 1H, OH), 8.45 (s, 1H, HCN), 7.11 (m, 1H, C6H4), 7.02−6.95 (m, 2H, C6H4), 6.69−6.63 (m, 4H, C6H4-C6H3). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 169.6 (CN), 162.2 (C−OH), multiplets from 157.5 to 154.9 (C−F, due to complicated 13C−19F coupling), 134.2, 133.2, 126.7, 126.0, 119.6, 119.2, 117.8, 112.3, 112.0 (Ar−C). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −123.7 (s, 2F, o-F). Anal. Calcd for C13H9F2NO (233.22 g/mol): C 66.95, H 3.89, N 6.01. Found: C 67.09, H 3.59, N 6.19. Synthesis of (2,3-C6H3F2NCHC6H4OH), {Ld}H. As described for {La}H but using 2,3-difluoroaniline (3.954 g, 0.030 mol) and 2hydroxybenzaldehyde (3.741 g, 0.030 mol). Yield: 5.976 g, 85%. 1H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 13.03 (s, 1H, OH), 7.88 (s, 1H, HCN), 7.05 (m, 2H, C6H3), 6.86 (d, 1H, C6H3), 6.65 (m, 1H, C6H4), 6.54 (m, 1H, C6H4), 6.40 (m, 1H, C6H4), 6.22 (m, 1H, C6H4). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 165.8 (C N), 162.0 (C−OH), multiplets from 152.6 to 138.5 (C−F, due to complicated 13C−19F coupling), 133.9, 132.7, 123.6, 119.0, 118.8, 117.7, 116.4, 114.6, 114.4 (Ar−C). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −137.1 (d, 1F, o-F), −150.5 (d, 1F, m-F). Anal. Calcd for C13H9F2NO (233.22 g/mol): C 66.95, H 3.89, N 6.01. Found: C 66.66, H 3.85, N 6.36. Synthesis of (2-C6H4FNCHC6H4OH), {Le}H. Using the same method as that for {La}H but employing a mixture of 2-fluoroaniline (3.097 g, 0.028 mol) and 2-hydroxybenzaldehyde (3.474 g, 0.028 mol). A yellow powder was isolated in high yield. Yield: 5.334 g, 89%. 1 H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 13.36 (s, 1H, OH), 8.02 (s, 1H, HCN), 7.06 (m, 2H, C6H4), 6.89 (m, 1H, C6H4), 6.82−6.59 (m, 5H, C6H4). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 165.0 (CN), 162.3 (C−OH), 157.4, 154.9 (C−F, due to complicated 13C−19F coupling), 136.9, 133.8, 132.8, 124.6, 121.7, 119.5, 118.9, 117.9, 116.5 (Ar−C). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −125.5 (s, 1F, o-F). Anal. Calcd for C13H10FNO F


Article

Organometallics K): δ 8.22 (s, 1H, HCN), 7.17 (bs, 1H, C6H4), 7.03 (bs, 1H, C6H4), 6.83 (m, 1H, C6H4), 6.45 (m, 1H, C6H4), 6.26 (m, 2H, C6H2). 13 C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 171.8 (CN), 169.5 (C−O), multiplets from 160.5 to 154.7 (C−F, due to complicated 13 C−19F coupling), 137.1, 134.5, 123.5, 122.6, 113.1, 100.6 (Ar−C). 19 F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −113.5 (bs, 2F, o-F), −122.2 (s, 1F, p-F). Anal. Calcd for C13H7F3LiNO (257.14 g/mol): C 60.72, H 2.74, N 5.45. Found: C 60.68, H 2.95, N 5.85. Synthesis of [Na(O-2-{(2,4,6-C6H2F3)NCH}C6H4)] [Na{Lb}] (2b). Following the same procedure as that described for 1a but using {Lb}H (1.005 g, 4.00 mmol) and NaH (0.096 g, 4.00 mmol). Yield: 1.045 g, 96%. 1H NMR (C6D6/THF-d8, 400 MHz): δ 8.14 (s, 1H, HCN), 7.02 (m, 1H, C6H4), 6.89 (m, 1H, C6H4), 6.65 (bs, 1H, C6H4), 6.36−6.27 (m, 3H, C6H4-C6H2). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 172.4 (CN), 169.1 (C−O), multiplets from 160.7 to 148.4 (C−F, due to complicated 13C−19F coupling), 136.9, 133.6, 130.5, 123.3, 111.3, 113.8, 100.1 (Ar−C). 19F NMR (C6D6/ THF-d8, 376 MHz, 295 K): δ −115.9 (bs, 1F, p-F), −125.1 (bs, 2F, oF). Anal. Calcd for C13H7F3NNaO (273.19 g/mol): C 57.16, H 2.58, N 5.13. Found: C 57.55, H 2.66, N 5.19. Synthesis of [K(O-2-{(2,4,6-C6H2F3)NCH}C6H4)] [K{Lb}] (3b). As described for 1a but with {Lb}H (1.000 g, 3.98 mmol) and K[N{Si(CH3)3}2] (0.836 g, 3.98 mmol). Yield: 1.017 g, 88%. 1H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 8.04 (s, 1H, HCN), 6.94 (m, 1H, C6H4), 6.77 (m, 1H, C6H4), 6.33 (m, 2H, C6H2), 6.19 (m, 1H, C6H4), 6.01 (m, 1H, C6H4). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 174.5 (C−O), 172.9 (CN), multiplets from 159.3 to 153.9 (C−F, due to complicated 13C−19F coupling), 137.0, 133.7 (Ar−C), multiplets from 130.5 to 129.3 (C−F, due to complicated 13 C−19F coupling), 123.3, 122.2, 109.7, 100.5 (Ar−C). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −117.2 (s, 1F, p-F), −126.3 (s, 2F, o-F). Anal. Calcd for C13H7F3KNO (289.30 g/mol): C 53.97, H 2.44, N 4.84. Found: C 54.22, H 2.81, N 4.93. Synthesis of [Li(O-2-{(2,6-C6H3F2)NCH}C6H4)] [Li{Lc}] (1c). As described for 1a but using {Lc}H (0.390 g, 1.67 mmol) and Li[N{Si(CH3)3}2] (0.288 g, 1.67 mmol). Yield: 0.325 g, 81%. 1H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 8.40 (bs, 1H, HCN), 6.94 (m, 3H, C6H4-C6H3), 6.37−6.27 (m, 4H, C6H4-C6H3). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 171.5 (CN), 169.3 (C−O), multiplets from 157.7 to 155.2 (C−F, due to complicated 13 C−19F coupling), 137.0, 134.4, 124.6, 123.6, 123.1, 114.5, 112.0, 111.8 (Ar−C). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −125.4 (s, 2F, o-F). Anal. Calcd for C13H8F2LiNO (239.15 g/mol): C 65.29, H 3.37, N 5.86. Found: C 65.42, H 3.63, N 5.97. Synthesis of [K(O-2-{(2,6-C6H3F2)NCH}C6H4)] [K{Lc}] (3c). Using the same procedure but employing {Lc}H (0.400 g, 1.72 mmol) and K[N{Si(CH3)3}2] (0.360 g, 1.72 mmol). Yield: 0.407 g, 88%. 1H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 8.14 (s, 1H, HCN), 6.99 (m, 1H, C6H4), 6.82 (m, 1H, C6H4), 6.55−6.43 (m, 3H, C6H3-C6H4), 6.19 (m, 2H, C6H3). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 174.9 (C−O), 172.3 (CN), multiplets from 157.0 to 154.5 (C−F, due to complicated 13C−19F coupling), 137.0, 133.8, 123.0, 122.6, 111.9, 111.5, 109.8 (Ar−C). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −143.1 (s, 2F, o-F). Anal. Calcd for C13H8F2KNO (271.31 g/mol): C 57.55, H 2.97, N 5.16. Found: C 57.83, H 2.76, N 5.03. Synthesis of [Li(O-2-{(2,3-C6H3F2)NCH}C6H4)] [Li{Ld}] (1d). Using the same method as that for 1a but with {Ld}H (0.390 g, 1.67 mmol) and Li[N{Si(CH3)3}2] (0.288 g, 1.67 mmol). Yield: 0.305 g, 76%. 1H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 8.14 (s, 1H, HCN), 7.21 (m, 1H, C6H4), 7.12 (d, 1H, C6H4), 6.93 (d, 1H, C6H4), 6.63−6.46 (m, 4H, C6H4-C6H3). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 172.0 (C−O), 168.3 (CN), multiplets from 152.8 to 143.4 (C−F, due to complicated 13C−19F coupling), 142.9, 137.0, 134.7, 123.9, 123.7, 122.6, 116.7, 113.0, 112.9 (Ar−C). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −138.5 (d, 1F, o-F), −153.1 (d, 1F, m-F). Anal. Calcd for C13H8F2LiNO (239.15 g/mol): C 65.29, H 3.37, N 5.86. Found: C 65.27, H 3.77, N 6.28. Synthesis of [Na(O-2-{(2,3-C6H3F2)NCH}C6H4)] [Na{Ld}] (2d). Using the same method as that for 1a but with {Ld}H (1.000

g, 4.29 mmol) and NaH (0.103 g, 4.29 mmol). Yield: 0.991 g, 91%. H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 8.02 (s, 1H, HCN), 7.09 (m, 1H, C6H4), 6.97 (m, 1H, C6H4), 6.77 (m, 1H, C6H3), 6.55 (m, 3H, C6H4-C6H3), 6.38 (m, 1H, C6H3). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 172.4 (C−O), 168.3 (CN),155.9 (Ar−C), multiplets from 149.7 to 143.8 (C−F, due to complicated 13C−19F coupling), 136.8, 133.8, 123.7, 123.3, 115.9, 112.2, 111.5 (Ar−C). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −138.4 (s, 1F, o-F), −155.7 (bs, 1F, m-F). Anal. Calcd for C13H8F2NNaO (255.20 g/ mol): C 61.18, H 3.16, N 5.49. Found: C 61.40, H 3.23, N 5.55. Synthesis of [K(O-2-{(2,3-C6H3F2)NCH}C6H4)] [K{Ld}] (3d). As described above for compound 1a and using {Ld}H (0.600 g, 2.57 mmol) and K[N{Si(CH3)3}2] (0.540 g, 2.57 mmol). Yield: 0.663 g, 95%. 1H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 8.13 (s, 1H, HCN), 7.14 (m, 1H, C6H3), 6.69−6.54 (m, 5H, C6H4-C6H3), 6.29 (m, 1H, C6H4). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 174.3 (C−O), 168.2 (CN), multiplets from 152.6 to 143.3 (C−F, due to complicated 13C−19F coupling), 137.0, 134.1, 124.3, 123.8, 123.1, 116.6, 112.1, 111.9, 110.4 (Ar−C). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −139.2 (d, 1F, o-F), −154.5 (d, 1F, m-F). Anal. Calcd for C13H8F2KNO (271.31 g/mol): C 57.55, H 2.97, N 5.16. Found: C 57.22, H 3.14, N 5.08. Synthesis of [Li(O-2-{(2-C6H4F)NCH}C6H4)] [Li{Le}] (1e). The same procedure as that described for 1a was followed but with {Le}H (1.000 g, 4.65 mmol) and Li[N{Si(CH3)3}2] (0.801 g, 4.65 mmol). Yield: 0.920 g, 90%. 1H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 8.27 (s, 1H, HCN), 7.19 (m, 1H, C6H4), 7.14 (bs, 1H, C6H4), 6.95−6.76 (m, 5H, C6H4), 6.45 (t, 1H, C6H4). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 171.9 (C−O), 167.0 (CN), multiplets from 157.9 to 155.4 (C−F, due to complicated 13C−19F coupling), 140.8, 136.8, 134.2, 125.8, 124.8, 123.8, 122.9, 121.2, 115.9, 112.5 (Ar−C). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −127.8 (s, 1F, o-F). Anal. Calcd for C13H9FLiNO (221.16 g/mol): C 70.60, H 4.10, N 6.33. Found: C 70.24, H 4.24, N 6.44. Synthesis of [Na(O-2-{(2-C6H4F)NCH}C6H4)] [Na{Le}] (2e). As described for 1a but using {Le}H (1.000 g, 4.64 mmol) and NaH (0.111 g, 4.64 mmol). A yellow powder was obtained. Yield: 0.946 g, 86%. 1H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 8.03 (s, 1H, HCN), 7.11 (m, 1H, C6H4), 6.93 (m, 2H, C6H4), 6.70 (m, 4H, C6H4), 6.42 (bs, 1H, C6H4). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 166.7 (CN), 157.5 (C−O), multiplets from 150.1 to 149.2 (C−F, due to complicated 13C−19F coupling), 137.2, 133.7, 133.3, 125.1, 124.3, 123.6, 119.9, 115.5, 110.9 (Ar−C). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −132.2 (s, 1F, o-F). Anal. Calcd for C13H9FNNaO (237.21 g/mol): C 65.83, H 3.82, N 5.90. Found: C 65.78, H 3.56, N 5.80. Synthesis of [K(O-2-{(2-C6H4F)NCH}C6H4)] [K{Le}] (3e). As described for 1a but using {Le}H (1.000 g, 4.64 mmol) and K[N{Si(CH3)3}2] (0.976 g, 4.64 mmol). Yield: 0.917 g, 80%. 1H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 8.09 (s, 1H, HCN), 7.12 (m, 1H, C6H4), 6.97 (m, 1H, C6H4), 6.86−6.72 (m, 4H, C6H4), 6.54 (m, 1H, C6H4), 6.26 (m, 1H, C6H4). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 174.3 (C−O), 167.5 (CN), multiplets from 157.6 to 155.2 (C−F, due to complicated 13C−19F coupling), 143.3, 137.1, 133.9, 125.0, 124.7, 124.1, 123.4, 121.4, 115.6, 110.1 (Ar−C). 19 F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −128.8 (s, 1F, o-F). Anal. Calcd for C13H9FKNO (253.32 g/mol): C 61.64, H 3.58, N 5.53. Found: C 61.28, H 3.61, N 5.57. Synthesis of [Li(O-2-{(2-CF3C6H4CH2)NCH}C6H4)] [Li{Lf}] (1f). Using the same method as that for 1a but with {Lf}H (0.684 g, 2.45 mmol) and Li[N{Si(CH3)3}2] (0.423 g, 2.45 mmol). Yield: 0.583 g, 83%. 1H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 7.97 (s, 1H, HCN), 7.42−7.37 (m, 2H, ArH), 7.10−6.89 (m, 4H, ArH), 6.43 (bs, 2H, ArH), 4.57 (bs, 2H, −CH2−). 13C NMR (C6D6/THFd8, 101 MHz, 295 K): δ 169.1 (CN), 163.8 (C−O), 138.5, 136.0, 133.0, 132.5, 131.2 (Ar−C), 126.9 (CF3), 125.6, 124.0, 122.8, 112.2 (Ar−C), 62.1 (−CH2−). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −59.4 (s, 3F, CF3). Anal. Calcd for C15H11F3LiNO (285.19 g/ mol): C 63.17, H 3.89, N 4.91. Found: C 63.41, H 3.92, N 4.67. 1

G


Article

Organometallics Synthesis of [K(O-2-{(2-CF3C6H4CH2)NCH}C6H4)] [K{Lf}] (3f). As described for 1a but with {Lf}H (0.502 g, 1.80 mmol) and K[N{Si(CH3)3}2] (0.378 g, 1.80 mmol). Yield: 0.386 g, 68%. 1H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 8.20 (s, 1H, HCN), 7.41 (m, 2H, C6H4), 7.22 (bs, 1H, C6H4), 7.05−6.92 (m, 3H, C6H4), 6.54 (bs, 1H, C6H4), 6.38 (m, 1H, C6H4), 4.69 (bs, 2H, −CH2−). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 168.2 (CN), 164.6 (C−O), 139.7, 135.2, 133.0, 132.7, 130.5, 129.5(Ar−C), 127.0 (CF3), 126.0, 124.0, 123.2, 121.8, 111.2 (Ar−C), 62.4 (−CH2−). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −59.6 (s, 3F, CF3). Anal. Calcd for C15H11F3KNO (317.04 g/mol): C 56.77, H 3.49, N 4.41. Found: C 56.39, H 3.65, N 4.58. Synthesis of [Li(O-2-{(CF3CH2)NCH}C6H4)] [Li{Lg}] (1g). Using the same method as that for 1a but with {Lg}H (0.486 g, 2.39 mmol) and Li[N{Si(CH3)3}2] (0.412 g, 2.39 mmol). Yield: 0.410 g, 82%. 1H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 7.86 (s, 1H, HCN), 7.14 (m, 1H, C6H4), 7.02 (d, 1H, C6H4), 6.76 (d, 1H, C6H4), 6.42 (m, 1H, C6H4), 3.62 (m, 2H, −CH2−). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 172.9 (CN), 171.0 (C−O), 136.3, 134.0 (Ar−C), 127.0, 124.3 (CF3, due to complicated 13C−19F coupling), 123.3, 121.9, 112.3 (Ar−C), 62.2 (−CH2−). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −71.2 (s, 3F, CF3). Anal. Calcd for C9H7F3LiNO (209.10 g/mol): C 51.70, H 3.37, N 6.70. Found: C 51.40, H 3.52, N 6.51. Synthesis of [K(O-2-{(CF3CH2)NCH}C6H4)] [K{Lg}] (3g). As described above for compound 1a and using {Lg}H (0.421 g, 2.07 mmol) and K[N{Si(CH3)3}2] (0.435 g, 2.07 mmol). Yield: 0.266 g, 53%. 1H NMR (C6D6/THF-d8, 400 MHz, 295 K): δ 7.92 (s, 1H, HCN), 7.10 (m, 1H, C6H4), 7.02 (m, 1H, C6H4), 6.90 (m, 1H, C6H4), 6.66 (m, 1H, C6H4), 3.68 (m, 2H, −CH2−). 13C NMR (C6D6/THF-d8, 101 MHz, 295 K): δ 171.1 (C−O), 168.9 (CN), 133.6, 132.5 (Ar−C), 126.5, 123.7 (CF3, due to complicated 13C−19F coupling), 119.0, 118.7, 117.8 (Ar−C), 59.7 (−CH2−). 19F NMR (C6D6/THF-d8, 376 MHz, 295 K): δ −71.7 (s, 3F, CF3). Anal. Calcd for C9H7F3KNO (241.25 g/mol): C 44.81, H 2.92, N 5.81. Found: C 44.35, H 2.87, N 6.16. Synthesis of 6,7,8,9-Tetrafluorodibenz[b,f ][1,4]oxazepine (Ox1). At room temperature, a mixture of {La}H (0.530 g, 1.84 mmol) and K[N{Si(CH3)3}2] (0.387 g, 1.84 mmol) in toluene (50 mL) was stirred for one night. Volatile compounds were removed under vacuum, and the resultant solution was filtered and concentrated under reduced pressure and cooled at −20 °C, giving a yellow powder. This solid was filtered and dried under vacuum. Later, a little amount of THF or DMSO was added. A dark red solution was formed, and one single crystal was finally obtained and analyzed by X-ray diffraction. Yield: 0.440 g, 89%. 1H NMR (C6D6/ DMSO-d6, 400 MHz, 295 K): δ 8.59 (s, 1H, HCN), 7.34 (m, 2H, C6H4), 7.10 (m, 1H, C6H4), 7.01 (m, 1H, C6H4). 13C NMR (C6D6/ DMSO-d6, 101 MHz, 295 K): δ 164.1 (CN), 159.3 (C−O), multiplets from 143.7 to 137.1 (C−F, due to complicated 13C−19F coupling), 141.0, 134.9, 131.5, 127.2, 126.8, 121.0 (Ar−C). 19F NMR (C6D6/DMSO-d6, 376 MHz, 295 K): δ −148.4 (dd, 1F, C6F4), −158.7 (t, 1F, C6F4), −159.7 (dd, 1F, C6F4), −163.1 (t, 1F, C6F4). Anal. Calcd for C13H5F4NO (267.18 g/mol): C 58.44, H 1.89, N 5.24. Found: C 58.35, H 1.75, N 5.35. Synthesis of 7,9-Difluorodibenz[b,f ][1,4]oxazepine (Ox2). Following the same procedure as that described above but using {Lb}H (0.500 g, 1.99 mmol) and K[N{Si(CH3)3}2] (0.418 g, 1.99 mmol). After the addition of DMSO, 10 mL of hexane was added, and a dark yellow solid could be isolated. Yield: 0.391 g, 85%. 1H NMR (C6D6/DMSO-d6, 400 MHz, 295 K): δ 8.48 (s, 1H, HCN), 7.25 (m, 2H, C6H4), 7.01 (m, 2H, C6H4), 6.76 (m, 2H, C6H2). 13C NMR (C6D6/DMSO-d6, 101 MHz, 295 K): δ 161.7 (CN), 159.4 (C−O), multiplets from 163.3 to 156.7 (C−F, due to complicated 13C−19F coupling), 154.5, 134.2, 130.9, 127.4, 127.2, 126.2, 121.0, 105.2, 102.1 (Ar−C). 19F NMR (C6D6/DMSO-d6, 376 MHz, 295 K): δ −110.6 (d, 1F, C6H2F2), −115.4 (d, 1F, C6H2F2). Anal. Calcd for C13H7F2NO (231.20 g/mol): C 67.54, H 3.05, N 6.06. Found: C 67.23, H 2.81, N 6.11.

Synthesis of 9-Fluorodibenz[b,f ][1,4]oxazepine (Ox3). At room temperature, a mixture of {Lc}H (0.400 g, 1.72 mmol) and K[N{Si(CH3)3}2] (0.360 g, 1.72 mmol) in toluene (50 mL) was stirred for one night. Then, the complex was isolated under vacuum, and a little quantity of DMSO was added. After the reaction time, 5 mL of hexane was added. However, this compound is completely soluble in any solvent. In consequence, it was directly dried under vacuum. Yield: 0.329 g, 90%. 1H NMR (C6D6/DMSO-d6, 400 MHz, 295 K): δ 8.54 (s, 1H, HCN), 7.28 (m, 2H, C6H4), 7.02 (m, 3H, C6H4-C6H3), 6.86 (m, 2H, C6H4-C6H3). 13C NMR (C6D6/DMSO-d6, 101 MHz, 295 K): δ 162.3 (CN), 160.0 (C−O, C6H4), 159.2 (C− O, C6H3), 156.7, 154.4 (C−F, due to complicated 13C−19F coupling), 134.2, 130.8, 129.2, 127.6, 125.9, 120.9, 117.2, 113.4, 113.2 (Ar− C).19F NMR (C6D6/DMSO-d6, 376 MHz, 295 K): δ −119.6 (s, 1F, C6H3F). Anal. Calcd for C13H8FNO (213.21 g/mol): C 73.23, H 3.78, N 6.57. Found: C 73.69, H 3.67, N 6.79. Synthesis of 6-Fluorodibenz[b,f ][1,4]oxazepine (Ox4). As described aboved but employing {Ld}H (0.400 g, 1.72 mmol) and K[N{Si(CH3)3}2] (0.360 g, 1.72 mmol). 1H NMR (C6D6/DMSO-d6, 400 MHz, 295 K): δ 8.51 (s, 1H, HCN), 7.30 (m, 2H, ArH), 7.05− 6.96 (m, 5H, ArH). 13C NMR (C6D6/DMSO-d6, 101 MHz, 295 K): δ 161.9 (CN), 160.0 (C−O), 155.3, 152.8 (C−F, due to complicated 13 C−19F coupling), 142.9 (C−O), 134.2, 131.1, 127.5, 126.1, 125.7, 124.3, 120.8, 115.6, 115.4 (Ar−C).19F NMR (C6D6/DMSO-d6, 376 MHz, 295 K): δ −133.1 (s, 1F, C6H3F). Anal. Calcd for C13H8FNO (213.21 g/mol): C 73.23, H 3.78, N 6.57. Found: C 73.04, H 3.65, N 6.19. Single-Crystal X-ray Structure Determination for (2a·2THF) and Ox1. Data collection was performed at 200(2) K, with the crystals covered with perfluorinated ether oil. Single crystals of 1c were mounted on a Bruker-Nonius Kappa CCD single-crystal diffractometer equipped with a graphite-monochromated Mo−Kα radiation (λ = 0.71073 Å). Multiscan18 absorption correction procedures were applied to the data. The structure was solved using the WINGX package,19 by direct methods (SHELXS-97) and refined using full-matrix least-squares against F2 (SHELXL-16).20 All nonhydrogen atoms were anisotropically refined. Hydrogen atoms were geometrically placed and left riding on their parent atoms except for H7 in Ox1 that was found in the Fourier map and refined freely. As well, Ox1 showed some degree of twinning. For 2a, two disordered solvent molecules were present per each molecule of compound 2a. No chemical sense could be done of the disordered solvent molecule, so the squeeze procedure21 was applied to remove its contribution from the structure factors. As well, there is some disorder in the THF molecules bonded to the Na, that was not treated. Full-matrix leastsquares refinements were carried out by minimizing ∑w(Fo2 − Fc2)2 with the SHELXL-97 weighting scheme and stopped at shift/err < 0.001. The final residual electron density maps showed no remarkable features. Crystallographic data for the structures reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication nos. CCDC- 1881295 (2a· 2THF) and CCDC-1881296 (Ox1).

■

ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.8b00868. Characterization data for the synthesized compounds, details for the solid state structure determination, and NMR spectra (PDF) Accession Codes

CCDC 1881295 and 1881296 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The H


Article

Organometallics

F Bond Activation in Organic Synthesis. Chem. Rev. 2009, 109, 2119− 2183. (g) Ahrens, T.; Kohlmann, J.; Ahrens, M.; Braun, T. Functionalization of Fluorinated Molecules by Transition-MetalMediated C−F Bond Activation To Access Fluorinated Building Blocks. Chem. Rev. 2015, 115, 931−972. (h) Klahn, M.; Rosenthal, U. An Update on Recent Stoichiometric and Catalytic C−F Bond Cleavage Reactions by Lanthanide and Group 4 Transition-Metal Complexes. Organometallics 2012, 31, 1235−1244. (4) (a) Giffin, K. A.; Korobkov, I.; Baker, R. T. Bronsted acidpromoted C-F bond activation in [P,S]-ligated neutral and anionic perfluoronickelacyclopentanes. Dalton Trans. 2015, 44, 19587− 19596. (b) Chen, W.; Bakewell, C.; Crimmin, M. R. Functionalisation of Carbon-Fluorine Bonds with Main Group Reagents. Synthesis 2017, 49, 810−821. (c) Huang, W.; Diaconescu, P. L. Aromatic C−F Bond Activation by Rare-Earth-Metal Complexes. Organometallics 2017, 36, 89−96. (d) Deacon, G. B.; Forsyth, C. M.; Junk, P. C.; Wang, J. Intramolecular Metal-Fluorocarbon Coordination, C-F Bond Activation and Lanthanoid-Fluoride Clusters with Tethered Polyfluorophenylamide Ligands. Chem. - Eur. J. 2009, 15, 3082−3092. (e) Nova, A.; Mas-Balleste, R.; Ujaque, G.; González-Duarte, P.; Lledós, A. Csp3-F bond activation by nucleophilic attack of the {Pt2S2} core assisted by non-covalent interactions. Chem. Commun. 2008, 3130−3132. (f) Clot, E.; Eisenstein, O.; Jasim, N.; MacGregor, S. A.; McGrady, J. E.; Perutz, R. N. C-F and C-H Bond Activation of Fluorobenzenes and Fluoropyridines at Transition Metal Centers: How Fluorine Tips the Scales. Acc. Chem. Res. 2011, 44, 333−348. (g) Cano, J.; Sudupe, M.; Royo, P.; Mosquera, M. E. G. Evidence of Fluoride Transfer from the Anion of [Zr{C 5 H 3 [SiMe 2 (η 1 NtBu)]2}]+[RB(C6F5)3]− Complexes to the Zirconocenium Cation. Angew. Chem., Int. Ed. 2006, 45, 7572−7574. (h) Kiplinger, J. L.; Richmond, T. G.; Osterberg, C. E. Activation of Carbon-Fluorine Bonds by Metal Complexes. Chem. Rev. 1994, 94, 373−431. (i) Janjetovic, M.; Träff, A. M.; Hilmersson, G. Mild and Selective Activation and Substitution of Strong Aliphatic C − F Bonds. Chem. Eur. J. 2015, 21, 3772−3777. (j) Shen, C.; Wu, X.-F. Base-regulated tunable synthesis of pyridobenzoxazepinones and pyridobenzoxazines. Catal. Sci. Technol. 2015, 5, 4433−4443. (5) (a) Barrett, A. G. M.; Crimmin, M. R.; Hill, M. S.; Hitchcock, P. B.; Procopiou, P. A. Trifluoromethyl Coordination and C-F Bond Activation at Calcium. Angew. Chem., Int. Ed. 2007, 46, 6339−6342. (b) Deacon, G. B.; Junk, P. C.; Moxey, G. J. Synthesis of fluoro(aryloxo)alkaline earth metal cages by C-F bond activation. Dalton Trans. 2010, 39, 5620−5622. (c) Matsubara, K.; Ishibashi, T.; Koga, Y. C−F Bond-Cleavage Reactions of Fluoroalkanes with Magnesium Reagents and without Metal Catalysts. Org. Lett. 2009, 11, 1765−1768. (d) Hammann, J. M.; Unzner, T. A.; Magauer, T. A Transition-Metal-Free Synthesis of Fluorinated Naphthols. Chem. Eur. J. 2014, 20, 6733−6738. (e) Sun, C.-L.; Shi, Z.-J. TransitionMetal-Free Coupling Reactions. Chem. Rev. 2014, 114, 9219−9280. (f) Maddock, L. C. H.; Nixon, T.; Kennedy, A. R.; Probert, M. R.; Clegg, W.; Hevia, E. Utilising Sodium-Mediated Ferration for Regioselective Functionalisation of Fluoroarenes via C−H and C−F Bond Activations. Angew. Chem., Int. Ed. 2018, 57, 187−191. (6) (a) Xiang, S.-K.; Tan, W.; Zhang, D.-X.; Tian, X.-L.; Feng, C.; Wang, B.-Q.; Zhao, K.-Q.; Hu, P.; Yang, H. Synthesis of benzimidazoles by potassium tert-butoxide-promoted intermolecular cyclization reaction of 2-iodoanilines with nitriles. Org. Biomol. Chem. 2013, 11, 7271−7275. (b) Maity, P.; Ahammed, S.; Manna, R. N.; Ranu, B. C. Calcium mediated C-F bond substitution in fluoroarenes towards C-chalcogen bond formation. Org. Chem. Front. 2017, 4, 69− 76. (c) Diness, F.; Fairlie, D. P. Catalyst-Free N-Arylation Using Unactivated Fluorobenzenes. Angew. Chem., Int. Ed. 2012, 51, 8012− 8016. (d) Borch Jacobsen, C.; Meldal, M.; Diness, F. Mechanism and Scope of Base-Controlled Catalyst-Free N-Arylation of Amines with Unactivated Fluorobenzenes. Chem. - Eur. J. 2017, 23, 846−851. (e) Kong, X.; Zhang, H.; Xiao, Y.; Cao, C.; Shi, Y.; Pang, G. Effective, transition metal free and selective C-F activation under mild conditions. RSC Adv. 2015, 5, 7035−7048. (f) Li, H.; Wang, X.-Y.; Wei, B.; Xu, L.; Zhang, W.-X.; Pei, J.; Xi, Z. Intramolecular C−F and

Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

■

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (J.C.). *E-mail: [email protected] (M.E.G.M.). ORCID

Jesús Cano: 0000-0002-6643-7534 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS Dedicated to Prof. Dietmar Stalke on the occasion of his 60th birthday. We acknowledge MICINN (I3 program SPI1752XV0), UAH (CCG08-UAH/PPQ-4203 and UAH-AE-20172), and MINECO (CTQ201458270-R) projects for financial support. EU COST Action CA15106 (CHAOS). F.M.G-V. acknowledges the UAH for a fellowship.

■

REFERENCES

(1) (a) Naporra, F.; Gobleder, S.; Wittmann, H.-J.; Spindler, J.; Bodensteiner, M.; Bernhardt, G.; Hübner, H.; Gmeiner, P.; Elz, S.; Strasser, A. Dibenzo[b,f][1,4]oxazepines and dibenzo[b,e]oxepines: Influence of the chlorine substitution pattern on the pharmacology at the H1R, H4R, 5-HT2AR and other selected GPCRs. Pharmacol. Res. 2016, 113 (Part A), 610−625. (b) Wang, J.; Sanchez-Rosello, M.; Acena, J. L.; del Pozo, C.; Sorochinsky, A. E.; Fustero, S.; Soloshonok, V. A.; Liu, H. Fluorine in Pharmaceutical Industry: FluorineContaining Drugs Introduced to the Market in the Last Decade (2001−2011). Chem. Rev. 2014, 114, 2432−2506. (c) Cargill, M. R.; Sandford, G.; Tomlinson, D. J.; Hollfelder, N.; Pleis, F.; Nelles, G.; Kilickiran, P. Polyfluorinated cycloalkoxyphenyl ether systems as dopants for liquid crystal display applications. J. Fluorine Chem. 2011, 132, 829−833. (d) Berger, R.; Resnati, G.; Metrangolo, P.; Weber, E.; Hulliger, J. Organic fluorine compounds: a great opportunity for enhanced materials properties. Chem. Soc. Rev. 2011, 40, 3496−3508. (e) Purser, S.; Moore, P. R.; Swallow, S.; Gouverneur, V. Fluorine in medicinal chemistry. Chem. Soc. Rev. 2008, 37, 320−330. (f) Liao, Y.; Venhuis, B. J.; Rodenhuis, N.; Timmerman, W.; Wikstroem, H.; Meier, E.; Bartoszyk, G. D.; Boettcher, H.; Seyfried, C. A.; Sundell, S. New (Sulfonyloxy)piperazinyldibenzazepines as Potential Atypical Antipsychotics: Chemistry and Pharmacological Evaluation. J. Med. Chem. 1999, 42, 2235−2244. (g) Babudri, F.; Farinola, G. M.; Naso, F.; Ragni, R. Fluorinated organic materials for electronic and optoelectronic applications: the role of the fluorine atom. Chem. Commun. 2007, 1003−1022. (2) (a) O’Hagan, D. Understanding organofluorine chemistry. Chem. Soc. Rev. 2008, 37, 308−319. (b) Mazurek, U.; Schwarz, H. Carbonfluorine bond activation-looking at and learning from unsolvated systems. Chem. Commun. 2003, 1321−1326. (c) Blanksby, S. J.; Ellison, G. B. Bond dissociation energies of organic molecules. Acc. Chem. Res. 2003, 36, 255−263. (3) (a) Eisenstein, O.; Milani, J.; Perutz, R. N. Selectivity of C−H Activation and Competition between C−H and C−F Bond Activation at Fluorocarbons. Chem. Rev. 2017, 117, 8710−8753. (b) Stahl, T.; Klare, H. F. T.; Oestreich, M. Main-Group Lewis Acids for C−F Bond Activation. ACS Catal. 2013, 3, 1578−1587. (c) Shen, Q.; Huang, Y.G.; Liu, C.; Xiao, J.-C.; Chen, Q.-Y.; Guo, Y. Review of recent advances in C-F bond activation of aliphatic fluorides. J. Fluorine Chem. 2015, 179, 14−22. (d) Yin, H.; Zabula, A. V.; Schelter, E. J. CF→Ln/An interactions in synthetic f-element chemistry. Dalton Trans. 2016, 45, 6313−6323. (e) Nova, A.; Mas-Ballesté, R.; Lledós, A. Breaking C−F Bonds via Nucleophilic Attack of Coordinated Ligands: Transformations from C−F to C−X Bonds (X= H, N, O, S). Organometallics 2012, 31, 1245−1256. (f) Amii, H.; Uneyama, K. C− I


Article

Organometallics

of gem-difluoroalkenes with beta-keto thioamides. Org. Biomol. Chem. 2017, 15, 2436−2442. (9) (a) Allaway, C. L.; Daly, M.; Nieuwenhuyzen, M.; Saunders, G. C. Synthesis of polyfluorodibenz[b,f][1,4]oxazepines by the cyclization of 2-[(polyfluorobenzylidene)amino]phenols. J. Fluorine Chem. 2002, 115, 91−99. (b) Boivin, J.; Boutillier, P.; Zard, S. Z. An unusual and highly efficient access to thieno[2,3-b]-benzothiopyran structures. Tetrahedron Lett. 1999, 40, 2529−2532. (c) Shen, J.; Xue, L.; Lin, X.; Cheng, G.; Cui, X. The base-promoted synthesis of multisubstituted benzo[b][1,4]oxazepines. Chem. Commun. 2016, 52, 3292−3295. (d) Feng, J.-B.; Wu, X.-F. Base-promoted synthesis of dibenzoxazepinamines and quinazolinimines under metal-free conditions. Green Chem. 2015, 17, 4522−4526. (e) Ouyang, L.; Qi, C.; He, H.; Peng, Y.; Xiong, W.; Ren, Y.; Jiang, H. Base-Promoted Formal [4 + 3] Annulation between 2-Fluorophenylacetylenes and Ketones: A Route to Benzoxepines. J. Org. Chem. 2016, 81, 912−919. (f) Choi, Y. L.; Lim, H. S.; Lim, H. J.; Heo, J.-N. One-Pot Transition-Metal-Free Synthesis of Dibenzo[b,f]oxepins from 2-Halobenzaldehydes. Org. Lett. 2012, 14, 5102−5105. (10) (a) García-Valle, F. M.; Estivill, R.; Gallegos, C.; Cuenca, T.; Mosquera, M. E. G.; Tabernero, V.; Cano, J. Metal and LigandSubstituent Effects in the Immortal Polymerization of rac-Lactide with Li, Na, and K Phenoxo-imine Complexes. Organometallics 2015, 34, 477−487. (b) García-Valle, F. M.; Tabernero, V.; Cuenca, T.; Mosquera, M. E. G.; Cano, J.; Milione, S. Biodegradable PHB from rac-β-Butyrolactone: Highly Controlled ROP Mediated by a Pentacoordinated Aluminum Complex. Organometallics 2018, 37, 837−840. (c) Garcia-Valle, F. M.; Tabernero, V.; Cuenca, T.; Cano, J.; Mosquera, M. E. G. Schiff-base -ate derivatives with main group metals: generation of a tripodal aluminate metalloligand. Dalton Trans. 2018, 47, 6499−6506. (11) (a) Li, X.; Liu, Z.; Xu, Y.; Wang, D. Synthesis, crystal structure and hydrolysis activity of a novel heterobinuclear cobalt(III) sodium(I) Schiff base complex. J. Inorg. Biochem. 2017, 171, 37−44. (b) Search on Cambridge Structural Database, CSD version 5.39; May 2018. (12) (a) Lindeman, S. V.; Andrianov, V. G.; Kravcheni, S. G.; Potapov, V. M.; Potekhin, K. A.; Struchkov, Y. T. Crystal and molecular structures of the two crystalline modifications of Nsalicylidene-pentafluoroaniline. J. Struct. Chem. 1981, 22, 578−585. (b) Ahmad, J. U.; Nieger, M.; Sundberg, M. R.; Leskela, M.; Repo, T. Solid and solution structures of bulky tert-butyl substituted salicylaldimines. J. Mol. Struct. 2011, 995, 9−19. (c) Pang, W.; Zhao, J.-W.; Zhao, L.; Zhang, Z.-K.; Zhu, S.-Z. Synthesis, characterization and comparative study of a series of fluorinated Schiff bases containing different orientation CHN spacers. J. Mol. Struct. 2015, 1096, 21−28. (d) Makio, H.; Terao, H.; Iwashita, A.; Fujita, T. FI Catalysts for Olefin Polymerization-A COrnprehensive Treatment. Chem. Rev. 2011, 111, 2363−2449. (e) Iwasa, N.; Katao, S.; Liu, J.; Fujiki, M.; Furukawa, Y.; Nomura, K. Notable Effect of Fluoro Substituents in the Imino Group in Ring-Opening Polymerization of ε-Caprolactone by Al Complexes Containing Phenoxyimine Ligands. Organometallics 2009, 28, 2179−2187. (13) (a) Zhang, Q.; Zhang, W.; Wang, S.; Solan, G. A.; Liang, T.; Rajendran, N. M.; Sun, W.-H. Sodium iminoquinolates with cubic and hexagonal prismatic motifs: synthesis, characterization and their catalytic behavior toward the ROP of rac-lactide. Inorg. Chem. Front. 2016, 3, 1178−1189. (b) Lu, W.-Y.; Hsiao, M.-W.; Hsu, S. C. N.; Peng, W.-T.; Chang, Y.-J.; Tsou, Y.-C.; Wu, T.-Y.; Lai, Y.-C.; Chen, Y.; Chen, H.-Y. Synthesis, characterization and catalytic activity of lithium and sodium iminophenoxide complexes towards ring-opening polymerization of L-lactide. Dalton Trans. 2012, 41, 3659−3667. (14) (a) Aoyama, A.; Endo-Umeda, K.; Kishida, K.; Ohgane, K.; Noguchi-Yachide, T.; Aoyama, H.; Ishikawa, M.; Miyachi, H.; Makishima, M.; Hashimoto, Y. Design, Synthesis, and Biological Evaluation of Novel Transrepression-Selective Liver X Receptor (LXR) Ligands with 5,11-Dihydro-5-methyl-11-methylene-6H-dibenz b,e azepin-6-one Skeleton. J. Med. Chem. 2012, 55, 7360−7377. (b) Gijsen, H. J. M.; Berthelot, D.; Zaja, M.; Brone, B.; Geuens, I.;

C−H bond cleavage promoted by butadienyl heavy Grignard reagents. Nat. Commun. 2014, 5, 4508. (g) Bakewell, C.; White, A. J. P.; Crimmin, M. R. Addition of Carbon-Fluorine Bonds to a Mg(I)Mg(I) Bond: An Equivalent of Grignard Formation in Solution. J. Am. Chem. Soc. 2016, 138, 12763−12766. (h) Tang, X. Y.; Chang, J.; Liu, C. B.; Zhang, B. Base initiated aromatization/C-O bond formation: a new entry to O-pyrazole polyfluoroarylated ethers. Tetrahedron Lett. 2014, 55, 6534−6537. (i) Liu, C.; Cao, L.; Yin, X.; Xu, H.; Zhang, B. Selective C4−F bond cleavage/C−O bond formation of polyfluoroarenes with phenols and benzyl alcohols. J. Fluorine Chem. 2013, 156, 51−60. (j) Liu, C. B.; Zhang, B. Facile Access to Fluoroaromatic Molecules by Transition-Metal-Free C-F Bond Cleavage of Polyfluoroarenes: An Efficient, Green, and Sustainable Protocol. Chem. Rec. 2016, 16, 667−687. (k) Lin, Y.; Li, M.; Ji, X.; Wu, J.; Cao, S. n-Butyllithium-mediated synthesis of N-aryl tertiary amines by reactions of fluoroarenes with secondary amines at room temperature. Tetrahedron 2017, 73, 1466−1472. (l) Zhang, Q.; Song, C.; Huang, H.; Zhang, K.; Chang, J. Cesium carbonate promoted cascade reaction involving DMF as a reactant for the synthesis of dihydropyrrolizino[3,2-b]indol-10-ones. Org. Chem. Front. 2018, 5, 80−87. (m) Xiong, Y.; Wu, J.; Xiao, S.; Xiao, J.; Cao, S. Noncatalytic Pyridyl-Directed Alkylation and Arylation Carbon−Fluorine Bond of Polyfluoroarenes with Grignard Reagents. J. Org. Chem. 2013, 78, 4599−4603. (7) (a) Korb, M.; Lang, H. Multi-Ferrocenyl Aryl Ethers − Applying Nucleophilic Aromatic Substitution Reactions to Aryl Fluorides. Eur. J. Inorg. Chem. 2017, 2017, 276−287. (b) Pawlas, J.; Begtrup, M. A One-Pot Access to 6-Substituted Phenanthridines from Fluoroarenes and Nitriles via 1,2-Arynes. Org. Lett. 2002, 4, 2687−2690. (c) Larrosa, I.; Da Silva, M. I.; Gómez, P. M.; Hannen, P.; Ko, E.; Lenger, S. R.; Linke, S. R.; White, A. J. P.; Wilton, D.; Barrett, A. G. M. Highly Convergent Three Component Benzyne Coupling: The Total Synthesis of ent-Clavilactone B. J. Am. Chem. Soc. 2006, 128, 14042−14043. (d) Jones, E. P.; Jones, P.; Barrett, A. G. M. Asymmetric Synthesis of α-Aryl Amino Acids; Aryne-Mediated Diastereoselective Arylation. Org. Lett. 2011, 13, 1012−1015. (e) Tadross, P. M.; Stoltz, B. M. A Comprehensive History of Arynes in Natural Product Total Synthesis. Chem. Rev. 2012, 112, 3550−3577. (f) Scott, V. J.; Celenligil-Cetin, R.; Ozerov, O. V. Roomtemperature catalytic hydrodefluorination of C(sp3)-F bonds. J. Am. Chem. Soc. 2005, 127, 2852−2853. (g) Chu, T.; Boyko, Y.; Korobkov, I.; Nikonov, G. I. Transition Metal-like Oxidative Addition of C-F and C-O Bonds to an Aluminum(I) Center. Organometallics 2015, 34, 5363−5365. (8) (a) Yang, J.; Mao, A.; Yue, Z.; Zhu, W.; Luo, X.; Zhu, C.; Xiao, Y.; Zhang, J. A simple base-mediated synthesis of diverse functionalized ring-fluorinated 4H-pyrans via double direct C-F substitutions. Chem. Commun. 2015, 51, 8326−8329. (b) Ichikawa, J.; Wada, Y.; Okauchi, T.; Minami, T. 5-endo-Trigonal cyclization of o-substituted gem-difluorostyrenes: syntheses of 2-fluorinated indoles, benzo[b]furans and benzo[b]thiophenes. Chem. Commun. 1997, 1537−1538. (c) Wada, Y.; Ichikawa, J.; Katsume, T.; Nohiro, T.; Okauchi, T.; Minami, T. Intramolecular Cyclizations of o-Substituted β,βDifluorostyrenes: Synthesis of 3-Fluorinated Isochromenes and Isothiochromenes. Bull. Chem. Soc. Jpn. 2001, 74, 971−977. (d) Fuchibe, K.; Takahashi, M.; Ichikawa, J. Substitution of Two Fluorine Atoms in a Trifluoromethyl Group: Regioselective Synthesis of 3-Fluoropyrazoles. Angew. Chem., Int. Ed. 2012, 51, 12059−12062. (e) Ichikawa, J.; Wada, Y.; Kuroki, H.; Mihara, J.; Nadano, R. Intramolecular cyclization of beta,beta-difluorostyrenes bearing an iminomethyl or a diazenyl group at the ortho position: synthesis of 3fluorinated isoquinoline and cinnoline derivatives. Org. Biomol. Chem. 2007, 5, 3956−3962. (f) Fujita, T.; Takazawa, M.; Sugiyama, K.; Suzuki, N.; Ichikawa, J. Domino C−F Bond Activation of the CF3 Group: Synthesis of Fluorinated Dibenzo[a,c][7]annulenes from 2(Trifluoromethyl)-1-alkenes and 2,2′-Diceriobiaryls. Org. Lett. 2017, 19, 588−591. (g) Zhang, X. X.; Wu, M. S.; Zhang, J.; Cao, S. Synthesis of N,N-disubstituted 2-aminothiophenes by the cyclization J


Article

Organometallics Mercken, M. Analogues of Morphanthridine and the Tear Gas Dibenz b,f 1,4 oxazepine (CR) as Extremely Potent Activators of the Human Transient Receptor Potential Ankyrin1 (TRPA1) Channel. J. Med. Chem. 2010, 53, 7011−7020. (c) Hallinan, E. A.; Hagen, T. J.; Husa, R. K.; Tsymbalov, S.; Rao, S. N.; Vanhoeck, J. P.; Rafferty, M. F.; Stapelfeld, A.; Savage, M. A.; Reichman, M. N-substituted dibenzoxazepines as analgesic PGE(2) antagonists. J. Med. Chem. 1993, 36, 3293−3299. (d) Ott, I.; Kircher, B.; Heinisch, G.; Matuszczak, B. Substituted pyridazino 3,4-b 1,5 benzoxazepin-5 (6H) ones as multidrug-resistance modulating agents. J. Med. Chem. 2004, 47, 4627−4630. (15) (a) De Munck, L.; Vila, C.; Pedro, J. R. Catalytic Asymmetric Reactions Involving the Seven-Membered Cyclic Imine Moieties Present in Dibenzo b,f 1,4 oxazepines. Eur. J. Org. Chem. 2018, 2018, 140−146. (b) Zhou, Y.; Zhu, J.; Li, B.; Zhang, Y.; Feng, J.; Hall, A.; Shi, J.; Zhu, W. Access to Different Isomeric Dibenzoxazepinones through Copper-Catalyzed C-H Etherification and C-N Bond Construction with Controllable Rearrangement. Org. Lett. 2016, 18, 380−383. (16) (a) Li, D. Y.; Keresztes, I.; Hopson, R.; Williard, P. G. Characterization of Reactive Intermediates by Multinuclear DiffusionOrdered NMR Spectroscopy (DOSY). Acc. Chem. Res. 2009, 42, 270−280. (b) Muñoz, M. a. T.; Urbaneja, C.; Temprado, M.; Mosquera, M. E. G.; Cuenca, T. Lewis acid fragmentation of a lithium aryloxide cage: generation of new heterometallic aluminium-lithium species. Chem. Commun. 2011, 47, 11757−11759. (c) Gallegos, C.; Camacho, R.; Valiente, M.; Cuenca, T.; Cano, J. Cyclopentadienylbased Mg complexes in the intramolecular hydroamination of aminoalkenes: mechanistic evidence for cationic versus neutral magnesium derivatives. Catal. Sci. Technol. 2016, 6, 5134−5143. (d) Keresztes, I.; Williard, P. G. Diffusion-ordered NMR spectroscopy (DOSY) of THF solvated n-butyllithium aggregates. J. Am. Chem. Soc. 2000, 122, 10228−10229. (17) Lu, F. A.; Sun, H. J.; Du, A. Q.; Feng, L.; Li, X. Y. Selective Alkylation and Arylation of C-F Bond with Grignard Reagents. Org. Lett. 2014, 16, 772−775. (18) Blessing, R. H. An empirical correction for absorption anisotropy. Acta Crystallogr., Sect. A: Found. Crystallogr. 1995, 51, 33−38. (19) Farrugia, L. J. WinGX and ORTEP for Windows: an update. J. Appl. Crystallogr. 2012, 45, 849−854. (20) (a) Sheldrick, G. M. A short history of SHELX. Acta Crystallogr., Sect. A: Found. Crystallogr. 2008, 64, 112−122. (b) Sheldrick, G. M. Crystal structure refinement with SHELXL. Acta Crystallogr., Sect. C: Struct. Chem. 2015, 71, 3−8. (21) (a) Spek, A. Single-crystal structure validation with the program PLATON. J. Appl. Crystallogr. 2003, 36, 7−13.

K


Intramolecular CâF Activation in Schiff-Base Alkali Metal Complexes

Recommend Documents

Intramolecular CâF Activation in Schiff-Base Alkali Metal Complexes